<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=div, initial-scale=1.0">
    <title>Document</title>
</head>
<style>.box {
        width: 200px;
        height: 200px;
        border: 3px solid black;
        background-color: red;
        transition-duration: 3s;
    }

    .box:hover {
        border-radius: 50%;
        background-color: black;
        border: 3px solid red;

    }
</style>

<body>
        <div class="box"></div>
       
</body>

</html>